Renshaw cells aren’t involved
within afferent, efferent reflex.
But instead, they are engage when you have
a contraction through alpha motor neurons.
So this is information being send down
the spinal cord to the alpha motor neuron
to get a constriction.
At the same time as getting the constriction
from the alpha motor neuron,
there is feedback that is then
stimulating the Renshaw cell.
That Renshaw cell that gets stimulated then
inhibits further alpha motor unit contraction.
So this is also is a preventive mechanism,
and this is helpful in reducing the amount of
force output and limiting the contraction duration.
It is spot that this Renshaw cells,
might be involve a little bit
when a person goes through
something like weight training.
They start to get stronger, quicker than they
are increasing the amount of the muscle mass.
So maybe you are releasing some of these
inhibition that is put on by a Renshaw cells.
Pain Withdraw Reflex
This is one of our more complicated reflexes.
And involves many aspects
including both sides or two limbs.
This revolves something like
stepping it on something painful.
We’ve all done these before. You step on
something that was really sharp.
There is a reflex that happens
that doesn’t involves the brain
just the spinal cord for
you to respond to these.
First, you have this
cutaneous pain receptor
which is usually a sharp pain
being sent up to the spinal cord.
That information is sensed at
the level of the spinal cord
and a reflex response results.
The first thing that happens is you have
a stimulation to the opposite leg.
And that stimulation is to extend
the quadriceps and relax the hamstrings.
On the leg that is being have the pain
stimulus, there is a withdraw reflex.
Meaning that you have a reduction
in the amount of alpha motor neurons
going to the quadriceps
and an increase are ones going to the hamstring
with your semimembranosus and tendinosis.
Why are muscle reflexes so important?
The main reason why muscle reflexes
are there is to prevent injury.
So we saw through things
like the stretch reflex.
Muscles spindle sensing
the amount of stretch
and then causing a contraction of that muscle
because it was being stretch too much.
In Golgi tendon organs, we have a response
where there is too much tension on a tendon.
Therefore we have to reduce the amount of tension.
You do that by relaxing the muscle that
is undergoing that increase intension
and contracting the opposite muscle group so that
you don’t have so much tension on that tendon.
With things like the pain reflex,
this is a response in which you need
to contract some muscles and relax others.
And you that all in that effort
to prevent yourself from falling.
So all these reflexes in combination
are there to protect the body
from getting injured or falling.